1. Field of the Invention
This invention relates to keyboards for computers and particularly to a keyboard with an array of light emitters and photodiodes arranged for interception of light beams by the fingers.
2. Prior Art and Information Disclosure
A major public health problem emerging with increasing use of the computer is repetitive motion stress syndrome which develops in a user as a result of long hours operating the keyboard. The problem is characterized by soreness of the joints in the fingers, hands and wrists. Severe onset of this condition can often only be remedied by an operation to open the carpal tunnel. Numerous devices have appeared on the market to relieve this source of stress.
One group of these devices has been directed toward support for the wrists and hands while performing the typing operation (see, e.g., U.S. Pat. No. 5,131,614 to Garcia, et al).
Another group of devices is directed toward uniquely shaped keyboards in which combinations of keys are depressed simultaneously to type the various characters. This arrangement is intended to enable the user to position his hands and wrists in the most relaxed position while operating the keys and reduce the distance that the user's hands must be moved in order to operate the keyboard (see, e.g., The BAT chordal keyboard from Infogrip Inc., Baton Rouge, La.).
Another group of inventions is directed toward electrically actuated keys that require less operating force than the oldstyle typewriter keys. A number of these inventions disclose arrays of photo diodes and light emitters in which the character is selected by depressing a key which interposes a barrier, aperture, or deflector into the path of the light beam. For example
U.S. Pat. No. 3,579,047 is for a keyboard in which each key has one or more barriers. Each barrier, in one position of the key is a barrier to one of a plurality of light beams such that depression of a key or combination of keys generates a coded message.
U.S. Pat. No. 3,758,785 is for a key and keyboard housing comprising a light source and detector associated with each key and mounted in the housing such that depression of the key interrupts the associated beam.
U.S. Pat. No. 4,379,968 and Reissue 33,422 are for a matrix of rows and columns of apertures, each arranged to slide by depression of a key to a position where it admits or interrupts light beams radiated toward a corresponding detector.
U.S. Pat. No. 4,860,008 discloses a keyboard comprising a plurality of keys arranged in rows and columns, a deflector associated with each key, a radiation emitter for each column, and a detector for each column--all arranged such that deflection of a key deflects the light beam from the corresponding column to the detector in the corresponding row.
U.S. Pat. No. 4,980,685 is for an array of colomns and rows of key operated light valves wherein interconnection between the members of the array is accomplished with optical fibers.
Each valve includes a sliding barrier that is interposed between opposing ends of a pair of optical fibers.
Each of these inventions involves depression of a key, thereby inherently requiring some application of force. Furthermore, the cost of manufacturing the keyboard must also include the cost of the individual keys and the associated actuating mechanisms.